{"id":31003,"date":"2026-09-15T09:05:40","date_gmt":"2026-09-15T01:05:40","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=31003"},"modified":"2026-09-16T08:40:21","modified_gmt":"2026-09-16T00:40:21","slug":"how-does-an-automatic-transfer-switch-work-ats-working-principle-sequence-of-operation","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/","title":{"rendered":"\u00bfC\u00f3mo funciona un conmutador autom\u00e1tico de transferencia? Principio de funcionamiento y secuencia de funcionamiento del ATS"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"31003\" class=\"elementor elementor-31003\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ae5d45d e-flex e-con-boxed e-con e-parent\" data-id=\"ae5d45d\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-5a29775 elementor-widget elementor-widget-html\" data-id=\"5a29775\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>\r\n#leeyee-ats-operation-guide{\r\n  --ats-blue:#004898;\r\n  --ats-blue-dark:#00366f;\r\n  --ats-pale:#f7fbff;\r\n  --ats-pale-2:#eef5ff;\r\n  --ats-text:#26323d;\r\n  --ats-muted:#5f6b76;\r\n  --ats-line:#d9e3ec;\r\n  --ats-green:#24784a;\r\n  --ats-amber:#9a6700;\r\n  --ats-red:#a83a32;\r\n  --ats-radius:10px;\r\n  max-width:840px;\r\n  margin:0 auto;\r\n  padding:8px 20px 56px;\r\n  color:var(--ats-text);\r\n  font-size:17px;\r\n  line-height:1.72;\r\n  box-sizing:border-box;\r\n  overflow-wrap:anywhere;\r\n}\r\n\r\n#leeyee-ats-operation-guide *,\r\n#leeyee-ats-operation-guide *::before,\r\n#leeyee-ats-operation-guide *::after{\r\n  box-sizing:border-box;\r\n}\r\n\r\n#leeyee-ats-operation-guide p{\r\n  margin:0 0 18px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-kicker{\r\n  margin:0 0 12px;\r\n  color:var(--ats-blue);\r\n  font-size:14px;\r\n  font-weight:700;\r\n  letter-spacing:.055em;\r\n  text-transform:uppercase;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-intro{\r\n  margin-bottom:26px;\r\n  color:#34424f;\r\n  font-size:18px;\r\n  line-height:1.7;\r\n}\r\n\r\n#leeyee-ats-operation-guide h2{\r\n  margin:52px 0 18px;\r\n  color:#162735;\r\n  font-size:clamp(27px,3.1vw,33px);\r\n  line-height:1.22;\r\n  letter-spacing:-.018em;\r\n}\r\n\r\n#leeyee-ats-operation-guide h3{\r\n  margin:32px 0 12px;\r\n  color:#1d3344;\r\n  font-size:clamp(21px,2.4vw,25px);\r\n  line-height:1.3;\r\n}\r\n\r\n#leeyee-ats-operation-guide a:not(.leeyee-site-popup-btn){\r\n  color:var(--ats-blue);\r\n  text-decoration:underline;\r\n  text-decoration-thickness:1px;\r\n  text-underline-offset:3px;\r\n}\r\n\r\n#leeyee-ats-operation-guide strong{\r\n  color:#172b3b;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-ref{\r\n  white-space:nowrap;\r\n  font-size:.82em;\r\n  font-weight:700;\r\n  text-decoration:none !important;\r\n}\r\n\r\n\/* QUICK ANSWER *\/\r\n#leeyee-ats-operation-guide .ats-quick{\r\n  margin:26px 0 24px;\r\n  padding:25px 27px;\r\n  border-left:4px solid var(--ats-blue);\r\n  border-radius:0 var(--ats-radius) var(--ats-radius) 0;\r\n  background:var(--ats-pale);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-quick h2{\r\n  margin:0 0 13px;\r\n  font-size:25px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-quick p:last-child{\r\n  margin-bottom:0;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-sequence-line{\r\n  display:flex;\r\n  flex-wrap:wrap;\r\n  gap:7px 9px;\r\n  align-items:center;\r\n  margin:19px 0 0;\r\n  padding:0;\r\n  list-style:none;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-sequence-line li{\r\n  display:flex;\r\n  align-items:center;\r\n  gap:8px;\r\n  color:#34424f;\r\n  font-size:14px;\r\n  font-weight:650;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-sequence-line li:not(:last-child)::after{\r\n  content:\"\u2192\";\r\n  color:var(--ats-blue);\r\n  font-weight:800;\r\n}\r\n\r\n\/* KEY TAKEAWAYS *\/\r\n#leeyee-ats-operation-guide .ats-takeaways{\r\n  margin:0 0 34px;\r\n  padding:20px 22px;\r\n  border:1px solid #d3e1ec;\r\n  border-radius:9px;\r\n  background:#fff;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-takeaways strong{\r\n  display:block;\r\n  margin-bottom:9px;\r\n  color:var(--ats-blue-dark);\r\n  font-size:18px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-takeaways ul{\r\n  margin:0;\r\n  padding-left:22px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-takeaways li{\r\n  margin:6px 0;\r\n}\r\n\r\n\/* IMAGES *\/\r\n#leeyee-ats-operation-guide figure{\r\n  margin:30px 0 36px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-visual-wide{\r\n  width:calc(100% + 120px);\r\n  max-width:960px;\r\n  margin-left:-60px;\r\n}\r\n\r\n#leeyee-ats-operation-guide figure img{\r\n  display:block;\r\n  width:100%;\r\n  height:auto;\r\n  border:1px solid #e1e8ee;\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n#leeyee-ats-operation-guide figcaption{\r\n  max-width:800px;\r\n  margin:10px auto 0;\r\n  color:var(--ats-muted);\r\n  font-size:14px;\r\n  line-height:1.55;\r\n  text-align:center;\r\n}\r\n\r\n\/* TABLES *\/\r\n#leeyee-ats-operation-guide .ats-table-wrap{\r\n  width:100%;\r\n  margin:24px 0 12px;\r\n}\r\n\r\n#leeyee-ats-operation-guide table{\r\n  width:100%;\r\n  border-collapse:separate;\r\n  border-spacing:0;\r\n  border:1px solid var(--ats-line);\r\n  border-radius:9px;\r\n  overflow:hidden;\r\n  background:#fff;\r\n  font-size:15px;\r\n  line-height:1.5;\r\n}\r\n\r\n#leeyee-ats-operation-guide th,\r\n#leeyee-ats-operation-guide td{\r\n  padding:13px 14px;\r\n  border-right:1px solid var(--ats-line);\r\n  border-bottom:1px solid var(--ats-line);\r\n  vertical-align:top;\r\n  text-align:left;\r\n}\r\n\r\n#leeyee-ats-operation-guide th{\r\n  background:var(--ats-blue);\r\n  color:#fff;\r\n  font-weight:700;\r\n}\r\n\r\n#leeyee-ats-operation-guide th:last-child,\r\n#leeyee-ats-operation-guide td:last-child{\r\n  border-right:0;\r\n}\r\n\r\n#leeyee-ats-operation-guide tbody tr:last-child td{\r\n  border-bottom:0;\r\n}\r\n\r\n#leeyee-ats-operation-guide tbody tr:nth-child(even) td{\r\n  background:#fbfdff;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-table-note{\r\n  margin:10px 0 28px;\r\n  color:var(--ats-muted);\r\n  font-size:14px;\r\n}\r\n\r\n\/* CALLOUTS *\/\r\n#leeyee-ats-operation-guide .ats-note,\r\n#leeyee-ats-operation-guide .ats-buyer,\r\n#leeyee-ats-operation-guide .ats-warning{\r\n  margin:24px 0;\r\n  padding:19px 21px;\r\n  border-radius:9px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-note{\r\n  border:1px solid #cfe0ee;\r\n  background:var(--ats-pale);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-buyer{\r\n  border-left:4px solid var(--ats-blue);\r\n  background:#f8fbfe;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-warning{\r\n  border-left:4px solid #d49a2b;\r\n  background:#fffaf0;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-note strong,\r\n#leeyee-ats-operation-guide .ats-buyer strong,\r\n#leeyee-ats-operation-guide .ats-warning strong{\r\n  display:inline-block;\r\n  margin-bottom:4px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-note p:last-child,\r\n#leeyee-ats-operation-guide .ats-buyer p:last-child,\r\n#leeyee-ats-operation-guide .ats-warning p:last-child{\r\n  margin-bottom:0;\r\n}\r\n\r\n\/* LISTS *\/\r\n#leeyee-ats-operation-guide .ats-clean-list{\r\n  margin:14px 0 22px;\r\n  padding-left:23px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-clean-list li{\r\n  margin:7px 0;\r\n  padding-left:3px;\r\n}\r\n\r\n\/* SMALL EXPLANATION CARDS *\/\r\n#leeyee-ats-operation-guide .ats-definition-grid{\r\n  display:grid;\r\n  grid-template-columns:repeat(2,minmax(0,1fr));\r\n  gap:14px;\r\n  margin:22px 0 28px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-definition{\r\n  padding:18px 19px;\r\n  border:1px solid var(--ats-line);\r\n  border-radius:9px;\r\n  background:#fff;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-definition strong{\r\n  display:block;\r\n  margin-bottom:6px;\r\n  color:var(--ats-blue-dark);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-definition p{\r\n  margin:0;\r\n  font-size:15px;\r\n  line-height:1.58;\r\n}\r\n\r\n\/* TIMING FORMULA *\/\r\n#leeyee-ats-operation-guide .ats-formula{\r\n  margin:22px 0 28px;\r\n  padding:20px 22px;\r\n  border:1px solid #cfe0ee;\r\n  border-radius:9px;\r\n  background:var(--ats-pale-2);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-formula-title{\r\n  margin-bottom:10px;\r\n  color:var(--ats-blue-dark);\r\n  font-weight:750;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-formula-flow{\r\n  display:flex;\r\n  flex-wrap:wrap;\r\n  gap:7px;\r\n  align-items:center;\r\n  color:#34424f;\r\n  font-size:15px;\r\n  font-weight:600;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-formula-flow span:not(:last-child)::after{\r\n  content:\"+\";\r\n  margin-left:7px;\r\n  color:var(--ats-blue);\r\n  font-weight:800;\r\n}\r\n\r\n\/* CHECKLIST *\/\r\n#leeyee-ats-operation-guide .ats-checklist{\r\n  display:grid;\r\n  grid-template-columns:repeat(2,minmax(0,1fr));\r\n  gap:12px;\r\n  margin:23px 0 28px;\r\n  padding:0;\r\n  list-style:none;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-checklist li{\r\n  position:relative;\r\n  padding:14px 15px 14px 42px;\r\n  border:1px solid var(--ats-line);\r\n  border-radius:8px;\r\n  background:#fff;\r\n  font-size:15px;\r\n  line-height:1.48;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-checklist li::before{\r\n  content:\"\u2713\";\r\n  position:absolute;\r\n  left:15px;\r\n  top:13px;\r\n  color:var(--ats-blue);\r\n  font-weight:800;\r\n}\r\n\r\n\/* CTA *\/\r\n#leeyee-ats-operation-guide .ats-cta{\r\n  margin:33px 0 46px;\r\n  padding:27px 28px;\r\n  border:1px solid #cbddea;\r\n  border-radius:12px;\r\n  background:linear-gradient(180deg,#f8fcff 0%,#eef6fd 100%);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-cta h3{\r\n  margin:0 0 9px;\r\n  font-size:23px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-cta p{\r\n  margin-bottom:17px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-cta-actions{\r\n  margin-top:21px;\r\n}\r\n\r\n\/* POPUP BUTTON *\/\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light{\r\n  -webkit-appearance:none;\r\n  appearance:none;\r\n  display:inline-flex;\r\n  align-items:center;\r\n  justify-content:center;\r\n  min-height:48px;\r\n  max-width:100%;\r\n  margin:0;\r\n  padding:13px 24px;\r\n  border:1.5px solid var(--ats-blue);\r\n  border-radius:7px;\r\n  background:var(--ats-blue);\r\n  color:#fff;\r\n  box-shadow:0 4px 12px rgba(0,72,152,.14);\r\n  font-family:inherit;\r\n  font-size:16px;\r\n  font-weight:700;\r\n  line-height:1.25;\r\n  text-align:center;\r\n  text-decoration:none;\r\n  cursor:pointer;\r\n  transition:\r\n    background-color .2s ease,\r\n    border-color .2s ease,\r\n    box-shadow .2s ease,\r\n    transform .2s ease;\r\n}\r\n\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light .w-btn-label{\r\n  display:block;\r\n  color:inherit;\r\n  line-height:1.25;\r\n}\r\n\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light:hover{\r\n  border-color:var(--ats-blue-dark);\r\n  background:var(--ats-blue-dark);\r\n  color:#fff;\r\n  box-shadow:0 7px 18px rgba(0,72,152,.20);\r\n  transform:translateY(-1px);\r\n}\r\n\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light:focus,\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light:focus-visible{\r\n  outline:3px solid rgba(0,72,152,.18);\r\n  outline-offset:3px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .leeyee-about-btn-light:active{\r\n  transform:translateY(0);\r\n  box-shadow:0 3px 8px rgba(0,72,152,.15);\r\n}\r\n\r\n\/* RELATED *\/\r\n#leeyee-ats-operation-guide .ats-related{\r\n  margin:31px 0;\r\n  padding-top:21px;\r\n  border-top:1px solid var(--ats-line);\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-related strong{\r\n  margin-right:5px;\r\n}\r\n\r\n\/* FAQ *\/\r\n#leeyee-ats-operation-guide details{\r\n  margin:0;\r\n  border-bottom:1px solid var(--ats-line);\r\n}\r\n\r\n#leeyee-ats-operation-guide details:first-of-type{\r\n  border-top:1px solid var(--ats-line);\r\n}\r\n\r\n#leeyee-ats-operation-guide summary{\r\n  position:relative;\r\n  padding:17px 40px 17px 0;\r\n  cursor:pointer;\r\n  color:#1d3344;\r\n  font-weight:700;\r\n  line-height:1.45;\r\n  list-style:none;\r\n}\r\n\r\n#leeyee-ats-operation-guide summary::-webkit-details-marker{\r\n  display:none;\r\n}\r\n\r\n#leeyee-ats-operation-guide summary::after{\r\n  content:\"+\";\r\n  position:absolute;\r\n  right:5px;\r\n  top:14px;\r\n  color:var(--ats-blue);\r\n  font-size:24px;\r\n  font-weight:500;\r\n}\r\n\r\n#leeyee-ats-operation-guide details[open] summary::after{\r\n  content:\"\u2212\";\r\n}\r\n\r\n#leeyee-ats-operation-guide details .ats-faq-answer{\r\n  padding:0 10px 17px 0;\r\n  color:#46525d;\r\n}\r\n\r\n\/* REFERENCES *\/\r\n#leeyee-ats-operation-guide .ats-reference-list{\r\n  margin:18px 0 0;\r\n  padding-left:24px;\r\n  color:#4b5964;\r\n  font-size:14px;\r\n  line-height:1.6;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-reference-list li{\r\n  margin:10px 0;\r\n  padding-left:4px;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-reference-list a{\r\n  overflow-wrap:anywhere;\r\n}\r\n\r\n#leeyee-ats-operation-guide .ats-source-boundary{\r\n  margin-top:27px;\r\n  padding:17px 19px;\r\n  border-top:1px solid var(--ats-line);\r\n  border-bottom:1px solid var(--ats-line);\r\n  color:var(--ats-muted);\r\n  font-size:14px;\r\n  line-height:1.6;\r\n}\r\n\r\n\/* RESPONSIVE *\/\r\n@media (max-width:980px){\r\n  #leeyee-ats-operation-guide .ats-visual-wide{\r\n    width:100%;\r\n    margin-left:0;\r\n  }\r\n}\r\n\r\n@media (max-width:768px){\r\n  #leeyee-ats-operation-guide{\r\n    padding-left:18px;\r\n    padding-right:18px;\r\n    font-size:16px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide h2{\r\n    margin-top:43px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-definition-grid,\r\n  #leeyee-ats-operation-guide .ats-checklist{\r\n    grid-template-columns:1fr;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-quick,\r\n  #leeyee-ats-operation-guide .ats-cta{\r\n    padding:21px;\r\n  }\r\n}\r\n\r\n@media (max-width:600px){\r\n  #leeyee-ats-operation-guide{\r\n    padding-left:15px;\r\n    padding-right:15px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-intro{\r\n    font-size:17px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-sequence-line{\r\n    display:block;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-sequence-line li{\r\n    display:block;\r\n    position:relative;\r\n    margin:6px 0;\r\n    padding-left:19px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-sequence-line li::before{\r\n    content:\"\u2192\";\r\n    position:absolute;\r\n    left:0;\r\n    color:var(--ats-blue);\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-sequence-line li:not(:last-child)::after{\r\n    content:\"\";\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive,\r\n  #leeyee-ats-operation-guide table.ats-responsive tbody,\r\n  #leeyee-ats-operation-guide table.ats-responsive tr,\r\n  #leeyee-ats-operation-guide table.ats-responsive td{\r\n    display:block;\r\n    width:100%;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive{\r\n    border:0;\r\n    background:transparent;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive thead{\r\n    display:none;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive tr{\r\n    margin-bottom:13px;\r\n    border:1px solid var(--ats-line);\r\n    border-radius:8px;\r\n    overflow:hidden;\r\n    background:#fff;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive td{\r\n    padding:11px 13px;\r\n    border:0;\r\n    border-bottom:1px solid var(--ats-line);\r\n    background:#fff !important;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive td:last-child{\r\n    border-bottom:0;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide table.ats-responsive td::before{\r\n    content:attr(data-label);\r\n    display:block;\r\n    margin-bottom:3px;\r\n    color:var(--ats-blue);\r\n    font-size:12px;\r\n    font-weight:750;\r\n    letter-spacing:.03em;\r\n    text-transform:uppercase;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-formula-flow{\r\n    display:block;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-formula-flow span{\r\n    display:block;\r\n    margin:5px 0;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-formula-flow span:not(:last-child)::after{\r\n    content:\"\u2193\";\r\n    display:block;\r\n    margin:3px 0 0;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .leeyee-about-btn-light{\r\n    width:100%;\r\n    min-height:50px;\r\n    padding:14px 18px;\r\n  }\r\n}\r\n\r\n@media (max-width:430px){\r\n  #leeyee-ats-operation-guide{\r\n    padding-left:12px;\r\n    padding-right:12px;\r\n    line-height:1.68;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide .ats-quick,\r\n  #leeyee-ats-operation-guide .ats-takeaways,\r\n  #leeyee-ats-operation-guide .ats-note,\r\n  #leeyee-ats-operation-guide .ats-buyer,\r\n  #leeyee-ats-operation-guide .ats-warning,\r\n  #leeyee-ats-operation-guide .ats-cta,\r\n  #leeyee-ats-operation-guide .ats-formula{\r\n    padding:18px;\r\n  }\r\n\r\n  #leeyee-ats-operation-guide figure{\r\n    margin-top:24px;\r\n    margin-bottom:30px;\r\n  }\r\n}\r\n<\/style>\r\n\r\n<article id=\"leeyee-ats-operation-guide\">\r\n\r\n  <p class=\"ats-kicker\">ATS Working Principle &amp; Sequence of Operation<\/p>\r\n\r\n  <div class=\"ats-intro\">\r\n    <p>An automatic transfer switch does more than move electrical contacts from one power source to another. In a generator-backed system, the ATS must monitor the preferred source, decide whether that source remains acceptable, coordinate a generator start request, verify the alternate source, transfer the load, monitor utility recovery, retransfer the load and complete the generator cooldown sequence.<\/p>\r\n\r\n    <p>For panel builders, generator integrators, distributors, OEM buyers and project engineers, understanding this sequence is important because sensing functions, delays, transition method, interlocking and generator-control interfaces directly affect the ATS configuration required for a project.<\/p>\r\n  <\/div>\r\n\r\n  <section class=\"ats-quick\">\r\n    <div id=\"ez-toc-container\" class=\"ez-toc-v2_0_87 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#quick-answer-how-does-an-automatic-transfer-switch-work\" >Quick Answer: How Does an Automatic Transfer Switch Work?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#automatic-transfer-switch-sequence-of-operation-step-by-step\" >Automatic Transfer Switch Sequence of Operation: Step by Step<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#what-does-the-ats-monitor-before-it-transfers\" >What Does the ATS Monitor Before It Transfers?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#how-does-an-ats-start-the-generator\" >How Does an ATS Start the Generator?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#what-if-the-generator-does-not-start-or-the-backup-source-is-not-acceptable\" >What If the Generator Does Not Start or the Backup Source Is Not Acceptable?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#controller-switching-mechanism-and-interlock-who-does-what\" >Controller, Switching Mechanism and Interlock: Who Does What?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#why-ats-switching-time-is-not-total-power-restoration-time\" >Why ATS Switching Time Is Not Total Power Restoration Time<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#what-happens-when-utility-power-returns\" >What Happens When Utility Power Returns?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#open-delayed-and-closed-transition-what-happens-during-the-actual-transfer\" >Open, Delayed and Closed Transition: What Happens During the Actual Transfer?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#automatic-mode-vs-manual-mode\" >Automatic Mode vs Manual Mode<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#why-buyers-should-care-about-the-ats-working-principle\" >Why Buyers Should Care About the ATS Working Principle<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#what-should-a-buyer-confirm-before-ordering-an-ats\" >What Should a Buyer Confirm Before Ordering an ATS?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#standards-and-project-boundaries\" >Standards and Project Boundaries<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#frequently-asked-questions\" >Frequently Asked Questions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/#references\" >References<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"quick-answer-how-does-an-automatic-transfer-switch-work\"><\/span>Quick Answer: How Does an Automatic Transfer Switch Work?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p><strong>An automatic transfer switch works as a controlled power-transfer sequence.<\/strong> It monitors the preferred source and, if that source becomes unacceptable, follows programmed logic before transferring the load. In a utility-to-generator system, the controller can request generator start, verify that the alternate source has reached acceptable voltage and frequency conditions, and then command the switching mechanism to transfer the load. When utility power returns and satisfies the required return logic, the ATS retransfers the load and the generator can complete its cooldown sequence before stopping. <a class=\"ats-ref\" href=\"#ats-ref-1\">[1]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <ul class=\"ats-sequence-line\" aria-label=\"ATS sequence of operation summary\">\r\n      <li>Monitor utility<\/li>\r\n      <li>Detect unacceptable source<\/li>\r\n      <li>Request generator start<\/li>\r\n      <li>Verify backup source<\/li>\r\n      <li>Transfer load<\/li>\r\n      <li>Monitor utility return<\/li>\r\n      <li>Retransfer load<\/li>\r\n      <li>Generator cooldown<\/li>\r\n    <\/ul>\r\n  <\/section>\r\n\r\n  <div class=\"ats-takeaways\">\r\n    <strong>Key Takeaways<\/strong>\r\n    <ul>\r\n      <li><strong>ATS operation is a sequence, not one switching movement.<\/strong><\/li>\r\n      <li><strong>Generator start time and ATS switching time are different.<\/strong><\/li>\r\n      <li><strong>The controller decides when to transfer; the switching mechanism performs the transfer.<\/strong><\/li>\r\n      <li><strong>Retransfer normally occurs only after the preferred source satisfies the required return logic.<\/strong><\/li>\r\n      <li><strong>Open, delayed and closed transition produce different load-transfer behaviour.<\/strong><\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <figure class=\"ats-visual-wide\">\r\n    <img fetchpriority=\"high\"\r\n      src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/automatic-transfer-switch-sequence-of-operation.webp\"\r\n      alt=\"Automatic transfer switch sequence of operation from utility failure to generator start, load transfer, utility return, retransfer and generator cooldown\"\r\n      width=\"1448\"\r\n      height=\"1086\"\r\n      loading=\"eager\"\r\n      fetchpriority=\"high\"\r\n      decoding=\"async\">\r\n    <figcaption>The complete ATS sequence includes source monitoring, failure confirmation, generator start, alternate-source validation, transfer, utility recovery, retransfer and generator cooldown.<\/figcaption>\r\n  <\/figure>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"automatic-transfer-switch-sequence-of-operation-step-by-step\"><\/span>Automatic Transfer Switch Sequence of Operation: Step by Step<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>The easiest way to understand the ATS working principle is to follow one complete utility failure and recovery cycle. Exact timer names, source-acceptance thresholds and available functions vary by controller, so the final operating sequence must always be verified against the selected ATS, generator documentation and project requirements. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <div class=\"ats-table-wrap\">\r\n      <table class=\"ats-responsive\">\r\n        <thead>\r\n          <tr>\r\n            <th>Stage<\/th>\r\n            <th>What Happens<\/th>\r\n            <th>Buyer Meaning<\/th>\r\n          <\/tr>\r\n        <\/thead>\r\n        <tbody>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>1. Normal operation<\/strong><\/td>\r\n            <td data-label=\"What Happens\">Utility or another preferred source supplies the load while the ATS monitors source conditions.<\/td>\r\n            <td data-label=\"Buyer Meaning\">The controller must match the source arrangement and electrical system.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>2. Source becomes unacceptable<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The controller detects that the preferred source is outside its configured acceptable conditions.<\/td>\r\n            <td data-label=\"Buyer Meaning\">A transfer condition does not have to mean complete zero-voltage failure.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>3. Failure confirmation \/ start logic<\/strong><\/td>\r\n            <td data-label=\"What Happens\">After applicable confirmation or start delay, the ATS controller requests generator start.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Confirm generator-start interface and required timing functions.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>4. Generator starts<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The generator controller carries out cranking, engine start and electrical output build-up.<\/td>\r\n            <td data-label=\"Buyer Meaning\">The ATS normally requests start; it does not mechanically crank the engine.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>5. Backup source becomes acceptable<\/strong><\/td>\r\n            <td data-label=\"What Happens\">Generator voltage and frequency satisfy the source-acceptance logic required for transfer.<\/td>\r\n            <td data-label=\"Buyer Meaning\">A running engine does not automatically mean the source is ready for the load.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>6. Load transfer<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The controller commands the switching mechanism to connect the load to the alternate source.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Transition architecture determines whether the load sees a break or controlled overlap.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>7. Backup operation<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The generator supplies the load while the ATS continues monitoring both source conditions.<\/td>\r\n            <td data-label=\"Buyer Meaning\">The ATS remains active after transfer and watches for utility recovery.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>8. Utility returns<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The controller detects that the preferred source has returned and evaluates whether it is acceptable.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Utility voltage reappearing does not necessarily cause immediate retransfer.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>9. Retransfer<\/strong><\/td>\r\n            <td data-label=\"What Happens\">After applicable return logic or retransfer delay, the switching mechanism reconnects the load to the preferred source.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Return timing helps avoid unnecessary cycling during unstable recovery.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Stage\"><strong>10. Cooldown and standby<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The generator may continue running unloaded for a configured cooldown period before stopping.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Cooldown is part of the generator-control sequence, not the physical transfer time.<\/td>\r\n          <\/tr>\r\n        <\/tbody>\r\n      <\/table>\r\n    <\/div>\r\n\r\n    <p class=\"ats-table-note\"><strong>Procurement conclusion:<\/strong> ask for the complete ATS sequence of operation, not only a quoted \u201ctransfer time.\u201d<\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"what-does-the-ats-monitor-before-it-transfers\"><\/span>What Does the ATS Monitor Before It Transfers?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>A simplified explanation often says that an ATS \u201cdetects a power failure.\u201d In practice, the controller determines whether a source is <strong>acceptable or unacceptable<\/strong> according to the sensing functions and settings provided by that controller.<\/p>\r\n\r\n    <p>Voltage and frequency are fundamental monitored parameters in many automatic transfer systems. More capable controllers can also monitor conditions such as undervoltage, overvoltage, underfrequency, overfrequency, phase loss, phase reversal or voltage unbalance. Eaton's ATC-900 is one example of a controller providing these functions. <a class=\"ats-ref\" href=\"#ats-ref-1\">[1]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a><\/p>\r\n\r\n    <div class=\"ats-buyer\">\r\n      <p><strong>Buyer meaning<\/strong><\/p>\r\n      <p>Do not define the requirement only as \u201ctransfer when power goes off.\u201d Confirm which electrical conditions must make a source unacceptable and whether the proposed ATS controller actually monitors those conditions.<\/p>\r\n    <\/div>\r\n\r\n    <p>The actual voltage, frequency, pickup, dropout and timing settings are <strong>product- and project-specific<\/strong>. They should be confirmed against the current controller manual, generator requirements and project engineering specification rather than copied from generic guidance.<\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"how-does-an-ats-start-the-generator\"><\/span>How Does an ATS Start the Generator?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>In a typical utility-to-generator system, the ATS controller does not mechanically crank the generator engine. It sends a <strong>generator start request<\/strong> through the intended control interface. The generator controller then carries out its own cranking, starting and voltage\/frequency build-up sequence.<\/p>\r\n\r\n    <p>Cummins transfer-switch application guidance separates these events: the transfer switch initiates the start request, the engine starts and accelerates, the alternate source becomes acceptable, and only then can the transfer sequence continue according to the configured logic. <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <figure class=\"ats-visual-wide\">\r\n      <img loading=\"lazy\"\r\n        src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-utility-generator-load-control-diagram.webp\"\r\n        alt=\"Utility generator ATS and load diagram showing electrical power paths and generator start control signal\"\r\n        width=\"1448\"\r\n        height=\"1086\"\r\n        loading=\"lazy\"\r\n        decoding=\"async\">\r\n      <figcaption>The load-current path and the controller signal path are different. The exact start interface and terminals must be verified from the selected ATS and generator documentation.<\/figcaption>\r\n    <\/figure>\r\n\r\n    <div class=\"ats-warning\">\r\n      <p><strong>Important distinction<\/strong><\/p>\r\n      <p>\u201cThe ATS starts the generator\u201d is common shorthand. For engineering and procurement, it is more accurate to say that the ATS <strong>requests generator start<\/strong>. This distinction matters when confirming dry contacts, remote-start inputs, auxiliary power and generator-controller compatibility.<\/p>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"what-if-the-generator-does-not-start-or-the-backup-source-is-not-acceptable\"><\/span>What If the Generator Does Not Start or the Backup Source Is Not Acceptable?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p><strong>Generator running does not automatically mean generator acceptable for transfer.<\/strong> The ATS still needs the alternate source to satisfy the source-acceptance logic required by the controller before it commands transfer. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <p>If the generator fails to start, starts but does not build acceptable voltage or frequency, or becomes unstable before transfer, the ATS cannot simply assume that usable backup power is available.<\/p>\r\n\r\n    <p>The exact response can vary by equipment. Depending on the controller and system design, the ATS may remain in its present position, continue waiting, issue an alarm, record an event or follow another programmed sequence.<\/p>\r\n\r\n    <div class=\"ats-buyer\">\r\n      <p><strong>Buyer meaning<\/strong><\/p>\r\n      <p>For critical projects, ask the supplier what happens when the alternate source fails to become acceptable. Do not assume that every ATS has the same retry, alarm or fallback behaviour.<\/p>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"controller-switching-mechanism-and-interlock-who-does-what\"><\/span>Controller, Switching Mechanism and Interlock: Who Does What?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>An ATS becomes easier to understand when the <strong>decision-making function<\/strong> and the <strong>physical power-switching function<\/strong> are separated.<\/p>\r\n\r\n    <div class=\"ats-table-wrap\">\r\n      <table class=\"ats-responsive\">\r\n        <thead>\r\n          <tr>\r\n            <th>Part<\/th>\r\n            <th>Main Function<\/th>\r\n            <th>What a Buyer Should Confirm<\/th>\r\n          <\/tr>\r\n        <\/thead>\r\n        <tbody>\r\n          <tr>\r\n            <td data-label=\"Part\"><strong>ATS controller<\/strong><\/td>\r\n            <td data-label=\"Main Function\">Monitors source conditions and executes programmed transfer logic.<\/td>\r\n            <td data-label=\"What a Buyer Should Confirm\">Sensing functions, timers, operating modes, alarms and I\/O.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Part\"><strong>Switching mechanism<\/strong><\/td>\r\n            <td data-label=\"Main Function\">Physically carries current and changes the load connection between sources.<\/td>\r\n            <td data-label=\"What a Buyer Should Confirm\">Rated current, utilisation\/application requirements and transition mechanism.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Part\"><strong>Generator start interface<\/strong><\/td>\r\n            <td data-label=\"Main Function\">Passes the required start\/run request to the generator control system.<\/td>\r\n            <td data-label=\"What a Buyer Should Confirm\">Signal type and generator-controller compatibility.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Part\"><strong>Mechanical \/ electrical interlocking<\/strong><\/td>\r\n            <td data-label=\"Main Function\">In applicable designs, prevents unintended or prohibited source connection states.<\/td>\r\n            <td data-label=\"What a Buyer Should Confirm\">How source separation and interlocking are implemented.<\/td>\r\n          <\/tr>\r\n        <\/tbody>\r\n      <\/table>\r\n    <\/div>\r\n\r\n    <p>Eaton describes the switching mechanism as the part that physically carries rated current and changes the load connection from one source to another. Cummins documentation also describes mechanical and electrical interlocking used to prevent inadvertent source-to-source connection in applicable transfer-switch architectures. <a class=\"ats-ref\" href=\"#ats-ref-1\">[1]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-5\">[5]<\/a><\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"why-ats-switching-time-is-not-total-power-restoration-time\"><\/span>Why ATS Switching Time Is Not Total Power Restoration Time<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p><strong>The physical ATS switching action is only one part of the complete outage-to-restoration sequence.<\/strong> Before the switching mechanism can connect the load to the generator source, the system may first need to confirm the utility problem, request generator start, wait for the engine and alternator to build usable output, verify that the source is acceptable and complete any configured transfer delay. <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <div class=\"ats-formula\">\r\n      <div class=\"ats-formula-title\">Total restoration time may include:<\/div>\r\n      <div class=\"ats-formula-flow\">\r\n        <span>Failure confirmation<\/span>\r\n        <span>Generator starting<\/span>\r\n        <span>Source stabilization<\/span>\r\n        <span>Source acceptance<\/span>\r\n        <span>Transfer delay<\/span>\r\n        <span>Physical switching<\/span>\r\n      <\/div>\r\n    <\/div>\r\n\r\n    <figure class=\"ats-visual-wide\">\r\n      <img loading=\"lazy\"\r\n        src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-transfer-timing-sequence-diagram.webp\"\r\n        alt=\"ATS transfer timing diagram showing utility failure, generator start, source stabilization, transfer, utility recovery, retransfer delay and generator cooldown\"\r\n        width=\"1448\"\r\n        height=\"1086\"\r\n        loading=\"lazy\"\r\n        decoding=\"async\">\r\n      <figcaption>Generator startup, source validation and controller delays can take longer than the physical ATS switching action. Total restoration time and contact-transfer time are not the same measurement.<\/figcaption>\r\n    <\/figure>\r\n\r\n    <div class=\"ats-note\">\r\n      <p><strong>Do not specify a universal delay value.<\/strong><\/p>\r\n      <p>ATS controllers provide different timing functions and adjustment ranges. Appropriate values depend on controller design, generator characteristics, load behaviour, source stability and project requirements. Manufacturer manuals provide product-specific ranges; they are not universal settings. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"what-happens-when-utility-power-returns\"><\/span>What Happens When Utility Power Returns?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>The ATS normally continues monitoring the preferred source while the load is on generator power. When utility power returns, the controller evaluates whether the source has recovered to acceptable conditions before executing retransfer. <a class=\"ats-ref\" href=\"#ats-ref-1\">[1]<\/a><\/p>\r\n\r\n    <h3>Why use a return or retransfer delay?<\/h3>\r\n\r\n    <p>A return delay prevents the ATS from automatically transferring the load back simply because utility voltage reappears for a moment. The delay gives the control logic time to confirm that the preferred source satisfies the required recovery conditions.<\/p>\r\n\r\n    <p>This helps reduce repeated transfer and retransfer cycles during unstable utility recovery. The exact delay range, bypass functions and return logic depend on the controller and project configuration. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <h3>What is generator cooldown?<\/h3>\r\n\r\n    <p>After the load has returned to the preferred source, a generator-backed system may keep the engine running unloaded for a configured cooldown period before completing the stop sequence. Cummins identifies engine cooldown as a separate transfer-system timing function following retransfer. <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n\r\n    <div class=\"ats-buyer\">\r\n      <p><strong>Buyer meaning<\/strong><\/p>\r\n      <p>When comparing ATS controllers, ask about <strong>start delay, transfer delay, retransfer delay and engine cooldown separately<\/strong>. One headline \u201ctransfer time\u201d cannot describe the complete operating sequence.<\/p>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"open-delayed-and-closed-transition-what-happens-during-the-actual-transfer\"><\/span>Open, Delayed and Closed Transition: What Happens During the Actual Transfer?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>The transition method determines what happens electrically while the load moves from one source to the other. For buyers, this matters because motors, control systems, data equipment and other loads can respond differently to an interruption, intentional neutral period or controlled source overlap.<\/p>\r\n\r\n    <div class=\"ats-table-wrap\">\r\n      <table class=\"ats-responsive\">\r\n        <thead>\r\n          <tr>\r\n            <th>Transition Type<\/th>\r\n            <th>What Happens<\/th>\r\n            <th>Buyer Meaning<\/th>\r\n          <\/tr>\r\n        <\/thead>\r\n        <tbody>\r\n          <tr>\r\n            <td data-label=\"Transition Type\"><strong>Open transition<\/strong><\/td>\r\n            <td data-label=\"What Happens\">Source A opens before Source B closes: break before make.<\/td>\r\n            <td data-label=\"Buyer Meaning\">The load sees an interruption during transfer.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Transition Type\"><strong>Delayed transition<\/strong><\/td>\r\n            <td data-label=\"What Happens\">The load is disconnected from both sources for an intentional neutral interval before the second source is connected.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Useful where residual load voltage should decay before reconnection.<\/td>\r\n          <\/tr>\r\n          <tr>\r\n            <td data-label=\"Transition Type\"><strong>Closed transition<\/strong><\/td>\r\n            <td data-label=\"What Happens\">A controlled make-before-break sequence briefly overlaps suitable sources under defined conditions.<\/td>\r\n            <td data-label=\"Buyer Meaning\">Requires suitable ATS design, source conditions and system coordination.<\/td>\r\n          <\/tr>\r\n        <\/tbody>\r\n      <\/table>\r\n    <\/div>\r\n\r\n    <p>Schneider Electric \/ ASCO describes delayed transition as a transfer sequence with an intentional off or neutral interval between sources, while ABB also identifies open, delayed and closed transition as distinct transfer methods. <a class=\"ats-ref\" href=\"#ats-ref-4\">[4]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-8\">[8]<\/a><\/p>\r\n\r\n    <figure class=\"ats-visual-wide\">\r\n      <img loading=\"lazy\"\r\n        src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/open-vs-closed-transition-ats.webp\"\r\n        alt=\"Open transition versus closed transition automatic transfer switch comparison showing break-before-make and controlled make-before-break operation\"\r\n        width=\"1448\"\r\n        height=\"1086\"\r\n        loading=\"lazy\"\r\n        decoding=\"async\">\r\n      <figcaption>Open transition separates the two sources. Closed transition permits controlled overlap only when the equipment and source conditions support it. Delayed transition adds an intentional neutral interval between source connections.<\/figcaption>\r\n    <\/figure>\r\n\r\n    <div class=\"ats-warning\">\r\n      <p><strong>Closed transition does not mean every utility failure produces zero interruption.<\/strong><\/p>\r\n      <p>If the preferred utility source has already failed, there is no live normal source available to overlap with the generator. Schneider Electric \/ ASCO notes that transfer from a failed normal source to emergency power is therefore an open-transition event; closed transition is applicable when both sources are available and satisfy the required conditions. <a class=\"ats-ref\" href=\"#ats-ref-4\">[4]<\/a><\/p>\r\n    <\/div>\r\n\r\n    <p>Closed-transition capability is not simply a timer setting added to an ordinary switch. It requires suitable transfer equipment, control logic and system coordination. The current IEC 60947-6-1:2026 edition specifically includes requirements for ATSE having closed-transition capability. <a class=\"ats-ref\" href=\"#ats-ref-6\">[6]<\/a><\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"automatic-mode-vs-manual-mode\"><\/span>Automatic Mode vs Manual Mode<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>Operating-mode terminology can vary by manufacturer. Eaton, for example, distinguishes manual, non-automatic and automatic transfer arrangements. In an automatic arrangement, the controller senses source conditions and manages the transfer sequence. In other arrangements, an operator may initiate or physically perform part of the transfer process. <a class=\"ats-ref\" href=\"#ats-ref-1\">[1]<\/a><\/p>\r\n\r\n    <div class=\"ats-definition-grid\">\r\n      <div class=\"ats-definition\">\r\n        <strong>Automatic mode<\/strong>\r\n        <p>The controller monitors source conditions and initiates transfer according to its configured logic and available functions.<\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ats-definition\">\r\n        <strong>Manual \/ operator-initiated operation<\/strong>\r\n        <p>A person initiates or performs transfer according to the ATS design. Generator-start and control behaviour can vary by product.<\/p>\r\n      <\/div>\r\n    <\/div>\r\n\r\n    <p><strong>Project confirmation is required.<\/strong> Do not assume that putting an ATS into \u201cmanual\u201d mode disables every automatic function. Some controller designs can retain monitoring or generator-start functions while requiring human intervention for transfer. Check the selected controller manual.<\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"why-buyers-should-care-about-the-ats-working-principle\"><\/span>Why Buyers Should Care About the ATS Working Principle<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>Current rating alone does not tell you whether an ATS will behave correctly in the intended power system. Two switches with the same ampere rating can have very different sensing, timing, transition and control capabilities.<\/p>\r\n\r\n    <ul class=\"ats-clean-list\">\r\n      <li><strong>How quickly backup power can actually become available.<\/strong><\/li>\r\n      <li><strong>Which utility abnormalities should initiate the sequence.<\/strong><\/li>\r\n      <li><strong>Whether the generator control interface can receive the required start command.<\/strong><\/li>\r\n      <li><strong>Whether the load can tolerate open transition, requires a delayed neutral period, or needs another transfer method.<\/strong><\/li>\r\n      <li><strong>Whether start, transfer, retransfer and cooldown timing can be coordinated with the project.<\/strong><\/li>\r\n    <\/ul>\r\n\r\n    <p>This is why a technical buyer should request the <strong>controller functions and sequence of operation<\/strong>, not only the ampere rating, pole count and quoted transfer speed.<\/p>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"what-should-a-buyer-confirm-before-ordering-an-ats\"><\/span>What Should a Buyer Confirm Before Ordering an ATS?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>For a useful technical review, prepare the system information that directly affects the ATS operating sequence.<\/p>\r\n\r\n    <ul class=\"ats-checklist\">\r\n      <li><strong>Source arrangement:<\/strong> utility-generator, utility-utility or another approved configuration.<\/li>\r\n      <li><strong>System voltage and frequency.<\/strong><\/li>\r\n      <li><strong>Phase and neutral arrangement<\/strong> required by the electrical design.<\/li>\r\n      <li><strong>Continuous load current<\/strong> and relevant load characteristics.<\/li>\r\n      <li><strong>Generator start interface<\/strong> and generator-controller requirements.<\/li>\r\n      <li><strong>Required source-sensing functions<\/strong> such as voltage and frequency monitoring.<\/li>\r\n      <li><strong>Required transition type:<\/strong> open, delayed or closed transition where applicable.<\/li>\r\n      <li><strong>Required timing functions:<\/strong> start, transfer, retransfer and cooldown.<\/li>\r\n      <li><strong>Automatic, manual and test-mode requirements.<\/strong><\/li>\r\n      <li><strong>Interlocking and source-separation requirements.<\/strong><\/li>\r\n      <li><strong>Short-circuit coordination \/ withstand-and-closing requirements<\/strong> where applicable.<\/li>\r\n      <li><strong>Applicable standard, certification and market-access requirements.<\/strong><\/li>\r\n    <\/ul>\r\n\r\n    <div class=\"ats-cta\">\r\n      <h3>Need to Confirm an ATS Operating Sequence?<\/h3>\r\n      <p>Send the source arrangement, voltage and frequency, load type, generator interface, required transition method and timing requirements. LEEYEE can review the required operating logic against the proposed low-voltage ATS configuration.<\/p>\r\n      <p>Final selection must still be confirmed against the exact model datasheet, wiring diagram, certificate scope and project requirements.<\/p>\r\n\r\n      <div class=\"ats-cta-actions\">\r\n        <button type=\"button\" class=\"leeyee-about-btn-light leeyee-site-popup-btn\" aria-label=\"Request a Quote\">\r\n          <span class=\"w-btn-label\">Request a Quote<\/span>\r\n        <\/button>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"standards-and-project-boundaries\"><\/span>Standards and Project Boundaries<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>For IEC-based low-voltage projects, the current international transfer-switch standard is <strong>IEC 60947-6-1:2026, Edition 4.0<\/strong>, published in April 2026. It applies to transfer switching equipment used to transfer a load between supply sources at rated voltages not exceeding 1,000 V AC or 1,500 V DC. The 2026 edition also covers automatic transfer switching equipment, stand-alone ATS controllers and ATSE having closed-transition capability. <a class=\"ats-ref\" href=\"#ats-ref-6\">[6]<\/a><\/p>\r\n\r\n    <p>For North American applications, <strong>UL 1008<\/strong> is a key standard for transfer switch equipment, including automatic transfer switches used in applicable emergency and optional standby systems. <a class=\"ats-ref\" href=\"#ats-ref-7\">[7]<\/a><\/p>\r\n\r\n    <div class=\"ats-note\">\r\n      <p><strong>Certification scope must be checked by model.<\/strong><\/p>\r\n      <p>Mentioning a standard in this guide does not mean every LEEYEE ATS model or every ATS on the market is certified to that standard. Buyers should request the certificate, listing or test documentation applicable to the exact model and destination market.<\/p>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"frequently-asked-questions\"><\/span>Frequently Asked Questions<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <details>\r\n      <summary>Does an ATS start the generator automatically?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>In a typical utility-to-generator system, the ATS controller can send a generator start request after the preferred source becomes unacceptable and the applicable start logic is satisfied. The generator controller then carries out the actual engine-start process. <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Why doesn't an ATS transfer immediately after utility failure?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>The system may first need to confirm that the preferred source is unacceptable, start the generator, wait for the alternate source to become acceptable and complete the configured transfer logic. Exact settings depend on the ATS controller and project. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>How long does an automatic transfer switch take to transfer?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>There is no universal total time. Physical contact switching can be much shorter than the complete power-restoration sequence. Generator startup, voltage and frequency stabilization, source acceptance and controller delays can all add time before the load receives backup power.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>What is ATS return or retransfer delay?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>It is a controller timing function used before returning the load to the preferred source after that source becomes acceptable again. It helps avoid immediate retransfer during unstable utility recovery. The required value must be confirmed for the selected controller and project.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>What is the difference between open and delayed transition?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>Both avoid intentional simultaneous connection of the two sources, but delayed transition adds an intentional neutral or off interval before the second source is connected. This can be useful where residual voltage from motors or other loads should decay before reconnection. <a class=\"ats-ref\" href=\"#ats-ref-4\">[4]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-8\">[8]<\/a><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Does closed transition mean there is never a power interruption?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>No. If the normal source has already failed, it cannot participate in a controlled source overlap. Schneider Electric \/ ASCO explains that transfer from a failed normal source to emergency power is therefore an open-transition event. Closed-transition operation is applicable when both sources are available and satisfy the required conditions. <a class=\"ats-ref\" href=\"#ats-ref-4\">[4]<\/a><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>What happens if the generator does not reach acceptable voltage or frequency?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>The ATS should not be assumed to transfer merely because the generator engine is running. The alternate source normally must satisfy the controller's source-acceptance conditions. The exact alarm, waiting, retry or fallback behaviour must be verified from the selected ATS controller documentation. <a class=\"ats-ref\" href=\"#ats-ref-2\">[2]<\/a> <a class=\"ats-ref\" href=\"#ats-ref-3\">[3]<\/a><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Is manual mode the same on every automatic transfer switch?<\/summary>\r\n      <div class=\"ats-faq-answer\">\r\n        <p>No. Manual, non-automatic, test and automatic modes can behave differently between products. Confirm which source-monitoring, generator-start and transfer functions remain active in each mode before approving the ATS for a project.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n  <\/section>\r\n\r\n  <div class=\"ats-related\">\r\n    <strong>Related reading:<\/strong>\r\n    <a href=\"https:\/\/www.cnspd.com\/what-is-an-automatic-transfer-switch-how-ats-works-how-to-choose\/\">What Is an Automatic Transfer Switch? ATS Types and Selection Guide<\/a>\r\n  <\/div>\r\n\r\n  <section>\r\n    <h2><span class=\"ez-toc-section\" id=\"references\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <ol class=\"ats-reference-list\">\r\n      <li id=\"ats-ref-1\">\r\n        Eaton, <em>Fundamentals of Automatic Transfer Switches (ATS)<\/em>. Explains ATS control logic, source monitoring, operating arrangements, transfer sequence and switching mechanisms.\r\n        <a href=\"https:\/\/www.eaton.com\/sg\/en-us\/products\/low-voltage-power-distribution-control-systems\/automatic-transfer-switches\/automatic-transfer-switch-fundamentals.html\" target=\"_blank\" rel=\"noopener noreferrer\">Official source<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-2\">\r\n        Eaton, <em>Automatic Transfer Switch Controller ATC-900 Operation and Maintenance Manual<\/em>, Instruction Booklet IB140012EN. Documents source-status functions including undervoltage, overvoltage, underfrequency, overfrequency, voltage unbalance, phase loss and phase reversal.\r\n        <a href=\"https:\/\/www.eaton.com\/content\/dam\/eaton\/products\/low-voltage-power-distribution-controls-systems\/ats\/resources\/atsc9-ib140012en.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">Official PDF<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-3\">\r\n        Cummins, <em>Transfer Switch Application Manual<\/em>. Describes source monitoring, generator start request, transfer timing, retransfer logic and engine cooldown as distinct parts of the operating sequence.\r\n        <a href=\"https:\/\/www.cummins.com\/sites\/default\/files\/2024-08\/t011-Transfer-switch-application-manual.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">Official PDF<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-4\">\r\n        Schneider Electric \/ ASCO, technical guidance on transfer-switch transition methods and operating behaviour, including open, delayed and closed transition and the limitation of closed transition after loss of the normal source.\r\n        <a href=\"https:\/\/www.se.com\/us\/en\/work\/featured-articles\/what-is-a-transfer-switch\/\" target=\"_blank\" rel=\"noopener noreferrer\">Official source<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-5\">\r\n        Cummins, <em>B-Series CBL Bypass Isolation Transfer Switch<\/em>. Manufacturer documentation describing mechanical and electrical interlocking used in that transfer-switch architecture.\r\n        <a href=\"https:\/\/www.cummins.com\/en-apac\/transfer-switches\/products\/b-series-cbl-bypass-isolation-transfer-switch\" target=\"_blank\" rel=\"noopener noreferrer\">Official source<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-6\">\r\n        International Electrotechnical Commission, <em>IEC 60947-6-1:2026 \u2014 Low-voltage switchgear and controlgear \u2014 Part 6-1: Multiple function equipment \u2014 Transfer switching equipment<\/em>, Edition 4.0.\r\n        <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/90494\" target=\"_blank\" rel=\"noopener noreferrer\">IEC official publication page<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-7\">\r\n        UL Solutions, <em>Switch Certification and Evaluation Services<\/em>. Identifies UL 1008 for transfer switch equipment used in applicable emergency and optional standby systems.\r\n        <a href=\"https:\/\/www.ul.com\/services\/switch-certification-and-evaluation-services\" target=\"_blank\" rel=\"noopener noreferrer\">UL Solutions official source<\/a>\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-8\">\r\n        ABB, <em>Automatic Transfer Switches Technical White Paper<\/em>. Describes open, delayed and closed transition as distinct ATS transition methods and explains the role of an intentional neutral position in delayed transition.\r\n        <a href=\"https:\/\/library.e.abb.com\/public\/a0a6a4a06b204e7bbf5988e6d35ee364\/ATS%20white%20paper_1SCC303022C0201_20-09.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">ABB official PDF<\/a>\r\n      <\/li>\r\n    <\/ol>\r\n\r\n    <div class=\"ats-source-boundary\">\r\n      Technical limits, source-acceptance thresholds, timing values, generator interfaces, neutral switching, transition method, short-circuit coordination and certification requirements vary by ATS model and installation. Confirm the final design against the manufacturer's current documentation, the applicable standard edition, local requirements and the project engineering specification.\r\n    <\/div>\r\n  <\/section>\r\n\r\n<\/article>\r\n\r\n<script>\r\n  document.addEventListener('DOMContentLoaded', function () {\r\n    var aboutPopupButtons = document.querySelectorAll('.leeyee-site-popup-btn');\r\n\r\n    aboutPopupButtons.forEach(function (button) {\r\n      button.addEventListener('click', function () {\r\n        var realPopupTrigger = document.querySelector('.w-popup.ush_popup_1 .w-popup-trigger');\r\n\r\n        if (realPopupTrigger) {\r\n          realPopupTrigger.click();\r\n        } else {\r\n          window.open('https:\/\/www.cnspd.com\/contact\/', '_blank', 'noopener'); \r\n        } \r\n      }); \r\n    }); \r\n  });\r\n<\/script>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>ATS Working Principle &amp; Sequence of Operation An automatic transfer switch does more than move electrical contacts from one power source to another. In a generator-backed system, the ATS must monitor the preferred source, decide whether that source remains acceptable, coordinate a generator start request, verify the alternate source, transfer the load, monitor utility recovery,&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[490,1,422],"tags":[],"class_list":["post-31003","post","type-post","status-publish","format-standard","hentry","category-isolator-switching","category-news","category-industry-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>How Does an Automatic Transfer Switch Work? ATS Sequence Explained<\/title>\n<meta name=\"description\" content=\"Learn how an automatic transfer switch monitors utility power, starts a generator, verifies backup power, transfers the load, retransfers after utility recovery, and manages open, delayed and closed transition.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cnspd.com\/es\/how-automatic-transfer-switch-works\/\" \/>\n<meta property=\"og:locale\" content=\"es_ES\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How Does an Automatic Transfer Switch Work? 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